The present invention relates generally to telemetry systems and more specifically to a pulsed telemetry system for conserving operating power.
In many telemetry systems for transmitting multiple channels of data derived from various types of transducers it is necessary to use battery power due to remote or inaccessible locations of the transducers. Often the battery size requirements for extended operation of the system becomes prohibitively large thus dictating intermittent operation to conserve energy and reduce battery size. However, in many systems, particularly in FM transmission systems, it is desirable to maintain continuous transmission to maintain synchronous operation for proper data channel recognition and readout.
One particular system in which the above problems are encountered is in an FM telemetry system for transmitting data from a plurality of strain gauges mounted on the bed stirrer for a coal gasifier. The stirrer is driven by a shaft which extends down from the top of the gasifier housing and is driven to obtain both rotating and reciprocating motions, thereby requiring wireless data transmission therefrom. The strain gauge instrumentation is required to measure three types of stirrer shaft loading: torque, bending (requires 2 sets of gauges) and axial. Four strain gauge bridges are mounted on the stirrer shaft in a conventional manner to obtain these measurements. The strain gauge electronics, batteries, and an FM telemetry link including a multiplexer, modulator and transmitter are all mounted on the stirrer shaft.
The energy required for continuous strain gauge bridge excitation for continuous operation of the gasifier over extended periods of time would required batteries which are too large to be supported by the stirrer shaft. Further, due to temperature changes, battery decay and component aging the electronic system is subject to zero drift associated with these factors. Thus, it will be seen that there is a need for a pulse-excited, auto-zeroing multiple channel data transmission system for use in wireless data transmission systems.